The mechanism of cell transformation with Rous sarcoma virus (RSV) will be studied by various approaches including virus genetics, studies on the expression of virus genes in uninfected and infected cells, and investigation on the sites of integration. The formation of heterozygotes as precursors or recombinants will be examined in a variety of systems. The endogenous origin of genes of RAV-60 will be established with many independent isolates. The sites of integration and their dynamic exchanges will be examined in chicken cell cultures infected with several subgroups of avian leukosis-sarcoma viruses. Attempts will be made on the cell free translation of viral messenger RNA, particularly m-RNA for putative transforming proteins. BIBLIOGRAPHIC REFERENCES: Khoury, A. T. and Hanafusa, J.; Synthesis and integration of viral DNA in chicken cells at different times after infection with various multiplicities of avian oncornavirus. J. Virol. 18, 383 (1976). Wang, L. H., Duesburg, P. H., Kawai, S., and Hanafusa, H.; Location of envelope-specific and sarcoma-specific oligonucleotides on RNA of Schmidt-Ruppin Rous sarcoma virus. Proc. Nat. Acad. Sci., U.S.A. 73, 447 (1976).